A physicist who performed his PhD with the Nobel-prize-winning physicist Louis de Broglie has received this year’s £1m Templeton Prize, which is awarded for “progress toward research or discoveries about spiritual realities”. Bernard d’Espagnat, a French physicist and philosopher of science, won the prize for his work on the philosophical implications of quantum mechanics by laying the theoretical groundwork for experimentally testing the violation of Bell’s inequalities.

The Templeton Prize was established in 1972 by the late philanthropist Sir John Templeton. According to the Templeton Foundation, the award is intended to encourage the concept that resources and manpower are needed to accelerate progress in spiritual discoveries. Physicists have been particularly successful in recent years: former laureates include Michael Heller (2008), John Barrow (2006), Charles Townes (2005), George Ellis (2004), John Polkinghorne (2002), Freeman Dyson (2000) and Paul Davies (1995).

Born in 1921, d’Espagnat has spent his career working on the discrepancies between quantum mechanics and the common-sense way of thinking how the world works. He studied at the Ecole Polytechnique before doing a PhD in particle physics at the Institut Henri Poincare in Paris under the supervision of de Broglie. After spending seven years as a research scientist with Enrico Fermi at the University of Chicago in the US he was appointed a senior researcher at CERN until 1959 and helped with creating the lab’s famous theoretical division.

In a tangle

When d’Espagnat returned to Paris in the 1960s he became interested in verifying the theory of quantum mechanics. In 1964, John Bell, then working at Stanford University, published a theorem that showed it could be possible to check if the picture of the world as described by quantum mechanics was correct.

Bell showed that a particular combination of measurements performed on identically prepared pairs of particles would produce a numerical bound –today called a Bell’s inequality — that is satisfied by all physical theories. He also showed, however, that this bound is violated by the predictions of quantum physics for entangled particle pairs. Bell’s inequality thus opened up the possibility of testing specific underlying assumptions of physical theories

If Bell’s inequalities were violated, by showing that measurements performed on entangled particles can apparently have an instantaneous influence on one another — then quantum mechanics would be correct. Many physicists, including Albert Einstein, thought that quantum mechanics was incorrect, or incomplete, since it violated the principle of “locality” – that an object is only influenced by its immediate surroundings.

D’Espagnat worked on ways to experimentally test Bell’s inequalities and thus provide an answer to whether the theory of quantum mechanics or the principle of locality best described nature. “We had to make the test,” Bernhard d’Espagnat told physicsworld.com, “in order to check if quantum mechanics was indeed true.”

The proof finally came in 1981 when experiments on polarised photons by fellow countryman Alain Aspect, whom d’Espagnat worked closely with, showed that Bell’s inequalities were indeed violated and thus quantum mechanics is correct.

Big spender

D’Espagnat, 87, who was born a Catholic, is also a prolific writer having penned over 20 books, including a best-selling book in France, which explained to a non-specialists the implications of Bell’s inequalities for our understating of the physical world. In 1983 the book was published in English as In Search of Reality, the Outlook of a Physicist.

With the £1m award, d’Espagnat is planning to give a third to his family, a third to charity and the rest for research. “I have not decided yet how to spend the money for research, whether I will give it to a public or private university,” says d’Espagnat.

In a statement d’Espagnat said “I feel myself deeply in accordance with the Templeton Foundation’s great, guiding idea that science does shed light [on spirituality]. In my view it does so mainly by rendering unbelievable an intellectual construction claiming to yield access to the ultimate ground of things with the sole use of the simple, somewhat trivial notions everybody has.”